NED Abstract

Copyright by European Southern Observatory (ESO).
Reproduced by permission
2009A&A...505.1049S
Parkes H I observations of galaxies behind the southern Milky Way. II. The
Crux and Great Attractor regions (l ~ 289^degree^to 338^degree^)
Schroder, A. C.; Kraan-Korteweg, R. C.; Henning, P. A.
Abstract. As part of our programme to map the large-scale distribution of
galaxies behind the southern Milky Way, we observed 314
optically-selected, partially-obscured galaxies in the Zone of Avoidance
(ZOA) in the Crux and Great Attractor (GA) regions. An additional 29
galaxies were observed in the Vela ZOA survey region (because of the small
numbers they are not discussed any further). The observations were
conducted with the Parkes 64 m (210 ft) radio telescope, in a single-pixel
pointed mode, reaching an rms noise level of typically 2-6 mJy over the
velocity search range of 400 < v < 10 500 km s^-1^. A total of 162
galaxies were detected (plus 14 galaxies in the Vela region). The
detection rate is slightly higher than for the Hydra/Antlia region (52%
versus 45%) observed in the same way. This can be explained by the
prominence of the GA overdensity in the survey regions, which leads to a
relatively higher fraction of nearby galaxies. It is also evident from the
quite narrow velocity distribution (largely confined to 3000-6000 km
s^-1^) and deviates significantly from the expectation of a uniform galaxy
distribution for the given sensitivity and velocity range. No systematic
differences were found between detections and non-detections, in terms of
latitude, foreground extinction, or environment, except for the very
central part of the rich Norma cluster, where hardly any galaxies were
detected. A detailed investigation of the H I content of the galaxies
reveals strong H I deficiency at the core of the Norma cluster (within
about a 0.4 Abell radius), similar to what has been found in the Coma
cluster. The redshifts obtained by this observing technique result in a
substantial reduction of the so-called redshift ZOA. This is obvious when
analysing the large-scale structure of the new H I data in combination
with data from other (optical) ZOA redshift surveys. The lower latitude
detections provide further evidence of the extension of the Norma Wall,
across the ZOA, in particular its bending towards the Cen-Crux clusters
above the Galactic plane at slightly higher redshift, rather than a
straight continuation towards the Centaurus clusters.
Key words: catalogs, surveys, ISM: dust, extinction, galaxies: fundamental
parameters, radio lines: galaxies, cosmology: large-scale structure of
Universe